The invention relates to a method of controlling receipt of signals at a terminal of a communications system, in particular for a mobile radio communications system.
In radio communications systems, signals are exchanged between radio terminals and radio stations to base stations via a so called radio interface or air interface. Such radio terminals are mobile or stationary user terminals or user equipments (UE). The base stations or Node Bs are access stations that are associated with a land based communication network. Examples of known radio communication systems are second generation digital mobile radio communication systems such as global system for mobile communication (GSM), based on time division multiple access (TDMA) and providing data rates up to 100 kbit/s, or third generation digital mobile radio communication systems such as universal mobile telecommunication system (UMTS), based on code division multiple access (CDMA) with data rates up to 2 Mbit/s.
A new feature in current radio communication systems such as GSM, GSM edge radio access network (GERAN) and UMTS, UMTS terrestrial radio access network (UTRAN) is the provision of multimedia broadcast multicast service (MBMS). Radio bearers for multicast MBMS services are set up within a cell of a base station, if there are user equipments present in the cell with the particular MBMS service activated. One of the main differences between MBMS and previous services is that MBMS can be offered and used when the user equipment is in idle mode, i.e. without an established radio connection to the network. The service uses a point-to-multipoint connection, either in a multicast or broadcast mode. General principles of MBMS are described in the standard documents 3GPP TR 25.992, V1.2.0 (2003-01) “Multimedia Broad-cast Multicast Service (MBMS); UTRAN/GERAN Requirements”, TR 23.846, V6.1.0 (2003-01) “MBMS; Architecture and functional description (Release 6)”, TS 22.146, V6.6.0 (2004-10) “MBMS; Stage 1 (Release 6)” and TS 45.002, V6.6.0 (2004-05) “Multiplexing and multiple access on the radio path (Release 6).
With the introduction of MBMS in UTRAN, a significant amount of control information related to the MBMS configuration in the cell of a base station is provided on an MBMS control channel (MCCH). A UE is required to periodically read this MCCH based upon the provision of services in the cell for which the UE is registered. The information scheduling and further parameters of the MCCH are described in detail in the standard document 3GPP TS 25.346 V6.2.0 (2004-09), chapter 5.2.
However, existing UE behaviour specifies that a UE is required to periodically make measurements of the neighbour cells in order for a UE to choose the cell in which it should operate. These measurements require the UE to measure channels provided in other cells, but a single receiver UE is unable to measure these channels and listen in its own cells at the same time.
This problem is exacerbated if the period over which the MCCH is repeated is a multiple of the frequency of occurrence of the occasions when the UE is required to perform neighbour cell measurements.
Information provided on the MCCH is repeated over a period of time known as the modification period, as defined in the above TS 25.346. This time interval defines the period over which one static set of MCCH information is provided to the UE. Some information used for notification purposes may change over this period, but this is not significant. Information within a modification period is repeated a plurality of times, each repetition being known as a repetition period. Each modification period is an exact multiple of a repetition period.
At the start of each modification period an index is sent which contains information about which services ongoing in the cell have had some configuration parameters changed since the last modification period and which have remained the same. This index is sent in order to reduce the amount of time the UE is required to read MCCH each modification period. If the index is not correctly read, the UE must read the whole of MCCH until it has successfully read all information.
Therefore, a method for efficiently establishing new connections in situations described above is required.
Ericsson: “Measurement requirements and MBMS reception”; 3GPP TSG-RAN WG4 #32, R4-040437; 16-20 Aug. 2004; pages 1 to 11; XP002362097 describes the existence of the problem of the conflict between inter-frequency and inter-RAT measurement with MBMS decoding during MBMS sessions.
Siemens: “Measurement requirements and MBMS reception in Cell-FACH state”; 3GPP TSG RAN WG4 #32, R4-040413; 18-20 Aug. 2004; pages 1 to 5; XP002362098 describes a plurality of options for dealing with the impact of MBMS data loss on MBMS quality of service.